Buggy code:
public class CheckGroup < T > extends FormComponent < Collection < T > > implements IOnChangeListener { private static final long serialVersionUID = 1L ; public CheckGroup ( String id ) { } public CheckGroup ( String id , Collection < T > collection ) { } public CheckGroup ( String id , IModel < Collection < T > > model ) { } @ SuppressWarnings ( "unchecked" ) @ Override protected Collection < T > convertValue ( String [ ] values ) throws ConversionException { List < T > collection = new ArrayList < T > ( ) ; if ( ( values != null ) && ( ( values . length ) > 0 ) ) { for ( int i = 0 ; i < ( values . length ) ; i ++ ) { final String value = values [ i ] ; if ( value != null ) { Check < T > checkbox = ( ( Check < T > ) ( visitChildren ( Check . class , new Component . IVisitor < Check < T > > ( ) { public Object component ( Check < T > check ) { if ( String . valueOf ( check . getValue ( ) ) . equals ( value ) ) { return check ; } return CONTINUE_TRAVERSAL ; } } ) ) ) ; if ( checkbox == null ) { <START_BUG> throw new org . apache . wicket . WicketRuntimeException ( ( ( ( ( ( ( ( "submitted<seq2seq4repair_space>http<seq2seq4repair_space>post<seq2seq4repair_space>value<seq2seq4repair_space>[" + ( Strings . join ( "," , values ) ) ) + "]<seq2seq4repair_space>for<seq2seq4repair_space>CheckGroup<seq2seq4repair_space>component<seq2seq4repair_space>[" ) + ( CheckGroup . getPath ( ) ) ) + "]<seq2seq4repair_space>contains<seq2seq4repair_space>an<seq2seq4repair_space>illegal<seq2seq4repair_space>relative<seq2seq4repair_space>path<seq2seq4repair_space>" ) + "element<seq2seq4repair_space>[" ) + value ) + "]<seq2seq4repair_space>which<seq2seq4repair_space>does<seq2seq4repair_space>not<seq2seq4repair_space>point<seq2seq4repair_space>to<seq2seq4repair_space>a<seq2seq4repair_space>Check<seq2seq4repair_space>component.<seq2seq4repair_space>Due<seq2seq4repair_space>to<seq2seq4repair_space>this<seq2seq4repair_space>the<seq2seq4repair_space>CheckGroup<seq2seq4repair_space>component<seq2seq4repair_space>cannot<seq2seq4repair_space>resolve<seq2seq4repair_space>the<seq2seq4repair_space>selected<seq2seq4repair_space>Check<seq2seq4repair_space>component<seq2seq4repair_space>pointed<seq2seq4repair_space>to<seq2seq4repair_space>by<seq2seq4repair_space>the<seq2seq4repair_space>illegal<seq2seq4repair_space>value.<seq2seq4repair_space>A<seq2seq4repair_space>possible<seq2seq4repair_space>reason<seq2seq4repair_space>is<seq2seq4repair_space>that<seq2seq4repair_space>componment<seq2seq4repair_space>hierarchy<seq2seq4repair_space>changed<seq2seq4repair_space>between<seq2seq4repair_space>rendering<seq2seq4repair_space>and<seq2seq4repair_space>form<seq2seq4repair_space>submission." ) ) ; <END_BUG> } collection . add ( checkbox . getModelObject ( ) ) ; } } } return collection ; } @ Override public void updateModel ( ) { } @ Override protected void onComponentTag ( ComponentTag tag ) { } public final void onSelectionChanged ( ) { } protected void onSelectionChanged ( final Collection < ? extends T > newSelection ) { } protected boolean wantOnSelectionChangedNotifications ( ) { } @ Override protected boolean getStatelessHint ( ) { } }

Fix:
throw new org . apache . wicket . WicketRuntimeException ( ( ( ( ( ( ( ( "submitted<seq2seq4repair_space>http<seq2seq4repair_space>post<seq2seq4repair_space>value<seq2seq4repair_space>[" + ( Strings . join ( "," , values ) ) ) + "]<seq2seq4repair_space>for<seq2seq4repair_space>CheckGroup<seq2seq4repair_space>component<seq2seq4repair_space>[" ) + ( CheckGroup . getPath ( ) ) ) + "]<seq2seq4repair_space>contains<seq2seq4repair_space>an<seq2seq4repair_space>illegal<seq2seq4repair_space>relative<seq2seq4repair_space>path<seq2seq4repair_space>" ) + "element<seq2seq4repair_space>[" ) + value ) + "]<seq2seq4repair_space>which<seq2seq4repair_space>does<seq2seq4repair_space>not<seq2seq4repair_space>point<seq2seq4repair_space>to<seq2seq4repair_space>a<seq2seq4repair_space>Check<seq2seq4repair_space>component.<seq2seq4repair_space>Due<seq2seq4repair_space>to<seq2seq4repair_space>this<seq2seq4repair_space>the<seq2seq4repair_space>CheckGroup<seq2seq4repair_space>component<seq2seq4repair_space>cannot<seq2seq4repair_space>resolve<seq2seq4repair_space>the<seq2seq4repair_space>selected<seq2seq4repair_space>Check<seq2seq4repair_space>component<seq2seq4repair_space>pointed<seq2seq4repair_space>to<seq2seq4repair_space>by<seq2seq4repair_space>the<seq2seq4repair_space>illegal<seq2seq4repair_space>value.<seq2seq4repair_space>A<seq2seq4repair_space>possible<seq2seq4repair_space>reason<seq2seq4repair_space>is<seq2seq4repair_space>that<seq2seq4repair_space>component<seq2seq4repair_space>hierarchy<seq2seq4repair_space>changed<seq2seq4repair_space>between<seq2seq4repair_space>rendering<seq2seq4repair_space>and<seq2seq4repair_space>form<seq2seq4repair_space>submission." ) ) ;